Spark gap



Dec. 18, 1928. 1,696,157

E. s. FLARSHEIM SPARK GAP 4 Filed Jan. 18, 1927 xs Win/W `chargedcondenser circuits.

Patented Dec. 18, 1928.

UNITED STATES PATENT orifice.

EDIQVIN S. FLARSHEIM, OF CINCINNATI, OHIO, ASSIGNOR TO LIEBEL-FLARSHEIMCOMPANY, OF CINCINNATI, OHIO, A CORPORATION OF OHIO.

SPARK GAP.

`Application led January 18, 1927. Serial No. 161,931. Y

My invention relates to spark gaps, and particularly to spark gapsadapted to produce high frequencyoscillating currents in Other factorsbeing equal, the powerin charged condenser circuits varies with and iscontrolled by the spacing of the electrodes of the spark gap. Thesparkgap of this invention is articularly intended for use in electrical highfrequency currentwork, where the power, and the damping must be asdefinitely controllable as possible. `The gap disclosed is specificallydesigned for use in an electrical cutting` machine adapted to beutilized as the cutting instrumentality in surgical operations.

A machine of this nature employs a high tension electrical sparkemanating from a comparatively dull edge as a flesh, tissue, fat orcartilage cutting medium. The cutting power of the spark is dependent ontwo factors, the voltage and amperage (or power), and the nature of thecurrent, i. e. the damping. The tissue dehydrating power of the spark isalso dependent on these same two factors. The greater the damping thegreater' is the dehydrating power and the less the cutting power. Both.vthe dehydrating and the cutting effects vary directly with the amount ofpower used. In performing surgical operations it is necessary tomaintain these factors constant at any desired point over a timesufficient in extent to perform the operation. Any variation in thesefactors during the operation not only would be highly annoying, butmightcause failure in securing Athe desired results.

While spark gaps have been used to pro duce high frequency oscillatingcurrents in charged condenser circuits, they have notbeen used inelectrical cutting machines of this nature loi the reason that heat isgen erated as the spark leaps between the elecgi'iodes,` and theelectrodes consequently eX- v pand thereby lessening the gap. Thisaffects the power ot the current and the damping of the oscillations andrenders the conventional gap vwholly unfit for the above mentionedpurposes. Hence my invention is of primary importance in 4that it makespossible and safe the i employment oi a spark gap as both a functionaland` control instrumentality in cter'off electrosurgical apparatusesi.,siy, my invention is also et value vtemperature range.`

It is also obviously necessary to adjust the spacing of the electrodesvery accurately in all work of the nature described, where the power,and the damping of the electrical oscillations inust be accuratelycontrolled.

Therefore, another object of my invention is to provide in combinationwith the compensating mechanism above mentioned, minute adjustingmechanism by which the operator is enabled to determine and fix thedistance between Ithe electrodes with great eXactness and accuracy.

v .Other objects and certain advantagesv will be more fully set forth inthe description of the accompanying drawings, torming a part of thisspecification, in which: Figure l is a side view of the spark gap.Figure 2 is an end view of the spark gap. Figure 3 is a sectional viewtaken on line 3 3, Figure l, showing the relation ol' the electrodes andthe mechanism for adjusting the electrodes and thepeXpansion members asa part'of the adjustment niechamsm. Y

Figure l is a view taken the same as Figure 3 but showing a modifiedformel adjustment means.

The spark gap of' this invention comprises two electrodes, and combinedspacing and compensating element adjustable in length to determinethelength of the gap between the two electrodes, and possessed of acoellie cient of expansion selected with reference to the coeflicient ofexpansion of the electrodes, to maintain the electrodes the samedistance apart as the spark generates heat, and both the electrodes andthe spacer consequently expand. p' j The s acer can be adjusted eitherby means o.: a screw "rotated through reduced motion gearing, or thespacer can be adjusted by means of two screws of diderent pitch, thesimultaneous rotation of which produces reduced motion according `to thepitch differential. The preferred gap organization comprises compressionmeans which tends to close the gap and compensating spacing meanscontrolled through reduced motion mechanism operating' against saidcompression means to open the gap.

More specifically, a base 1 has secured 4thereto b7 means of screws 3.and nuts 5 two angular brackets, one a narrow bracket 6, the other awider bracket 'i'. The spark gap is mounted on these brackets, theadjustment mechanism being supported over the wider bracket, Compressionmeans are provided which tend to pressthe electrodes together. v@aidmeans comprises two sets of flexible plates or disks 8, two to a set.These disks have the additional function of radiating the heat from theelectrodes. One electrode is carried centrally by each set ofllexibledisks. These disks are held together by means of threeinsulating assembling posts 9, each assembling post extending looselythrough all four disks. Thus each set of disks carrying its electrode isinsulated from the opposing set. lVires (not shown) are connected in anydesirable way to the opposing sets and the gap thus incorporated in theelectric circuit.

Each assembling post consists of a hollow insulating c linder 10 whichextends through the disks S, a screw 11 which passes through the hollowcylinder, a washer 12 between the screw head and an outer disk, and anut 13 on the other endef the screw "ith an insulating washer 14;between the nut and the other outer disk.

As disclosed, there are three of these assembling posts, the lower twoof which are used to secure the disks to the wide bracket 7. The narrowbracket 6 is secured to the other outer disk by means of a screw 15. Thedisks are thus concentrically mounted and secured together by theseassembling posts. This construction constitutes the outer disks, themain compression elements, and the inner disk guide elements to keep theelectrodes in proper alignment. All the disks have attheir centers equalsized circular aperta Each pair of disks has an elect-rode holder 16mounted in these apertures between the disks. As disclosed, theseelectrode holders are circular and each has cut at each edge acircumferential shoulder or notch 17 into which the disks lit. Theseelectrode holders have also concentric hollow centers and in thesecenters are the electrodes 18 preferably being pressed into said centersand held also by solder. These electrodes have flanges 2O which seat indepressions in the electrode holder faces. These electrodes arepreferably of copper or other metal of good thermal conductivity, andare provided with faces 21 rif-tungsten. The electrodes project beyondthe holders to an extent that the opposing surfaces 21 may contact eachother.

The means for securing adjustable spacing between these electrodescomprises a spacing element 22 carried by one electrode holder which isadapted to bear against a porcelaii'i anvil QS carried bythe opposingelectrode holder thereby forcing the electrode holders and electrodesapart. This spacing element is adjusted in relation to its carryingelectrode holder by means of a recessed screw 24 in which it `is looselymounted and which in turn screws in and out of the electrode holder. lnorder to provide a delicate adjusting mechanism, the screw provided atits outer end with a large and narrow gear wheel 25 ,which intermesheswith a small but wide pinion 26 mounted on a shaft 27 which is passinothrough and is supported by the set of risks which carry the`corresponding electrode holder, About this shaft QT between the twodisks, is a coiled spring 28 under compression between two Yashers 29.A. pin 30 secures the shaft 27 against longitudinal displacement. Thisjournaling provides friction so that the pinion cannot be too easilyturned or accidentally turned. On the outer end of this pinion shaft isan adjustment knob 31 secured to the shaft.

The modification of the adjusting mecl1 anisln shown in Figure lcomprises a rod 35 which holds the spacing member against rotation.Instead of being imbedded in the adjustment screw, this spacing memberscrews into the adjustment screw, the thread 36 being opposite to butdifferent in pitch from the thread 37 between the adjustment screw andthe electrode carrier. The "adjustment screw has on its outer end a conuventional turning knob 3S secured thereto by means of a nut and washer.In operation, turning this knob ell'ects a very slight differentialmotion between the two screws, thereby permitting and effecting verydelicate and exact adjustment of the electrodes with relation to eachother.

In either case, as the electrodes become heated and expand.` therebytending to lessen the length of the sparkv gap between them, the spacingmember also expands forcing the electrode (.:airiers farther apartthereby compensating for said electrode ex pansion. The coefiicient ofexpansion oi. the material used, must be very carefully selected inorder to secure this relative permanence of setting. The farther thespacing member from the electrodes and, thc heat generated thereby, thehigher must be its coeflicient of expansion in order that it mayfunction properly as a compensating member.

bil

lll l) llo Thus, I provide a spark gap adapted to be adjusted throughreduced motion mechanism, and set with extreme accuracy, the gap alsoprovided with a compensating electrode spacer adapted toinaintain thelength of the gap constant over a wide temperature range.. v n

Having described my invention, I claim:

l. A spark gap comprising two electrodes, and an adjustable spacingmember determining and controlling the gap between said electrodes, saidspacing member exposed to the heat generated by the spark and adapted `texpand and compensate for the electrode expansion thereby maintainingthe gap relatively fixed over a wide temperature range.

2. A spark gap. comprising two opposing electrodes, a tension elementpressing said electrodes together, and a spacing member holding saidelectrodes apart, said spacing member having a coeilicient oil expansionadapted to compensate for the expansion of the electrodes when heated inorder to maintain a constant gap between the electrodes.

3. A spark gap comprising two opposing electrodes, a spacing membercontrolling the gap between the electrodes, said spacing memberpossessed of a coefficient of expansion adapted to compensate forelectrode eX- pansion and maintain the gap constant over a widetemperature range, a knob for adjusting said spacing member, and reducedmotion mechanism connecting said knob and spacing member in order toprovide for the delicate adjustment of the latter.

4. A spark gap comprising two electrodes, compression means tending toclose the gap, and compensating spacing means controlled through reducedmotion mechanism operating against said `compression means to open thegap.

5. A spark gap comprising a base having mounted thereon two opposingflexible disks, two opposing electrodes each carried by a disk andprojecting therefrom to a contacting extent, compensating spacing meansbetween said disks, said spacing means adapted to space the electrodesagainst the tension ot the disks, and means for imparting minute motionto said compensating electrode spacing means to determine the gapbetween said electrodes.

6. A spark gap comprising a base having mounted thereon two opposingflexible disks, two opposing electrodes each carried by a disk, andprojecting therefrom to a contacting extent, a screw carried by onedisk, an electrode spacer secured to said screw said spacer adapted tospace the electrodes against the tension of the disks as the screw isturned inwardly, a large gear wheel on the outer end of said screw, asmall pinion in mesh with said large gear` wheel, a shaft adapted toturn said small pinion, a friction-producing member associated with saidshaft to prevent said sha-itt iironi being too easily turned, and a knobon the outer end of said shaft adapted to turn the saine and transmitmotion to the electrode spacer through said specified reduced motionmechanism. A

j 7. A spark gap comprising a base having mounted thereon two sets oiopposing ilexprojecting therefrom to a contacting extent, an anvilcarried by one electrode carrie a screw vcarried by the other electrodeca rier, said screw opposite toV said anvil, a compensating electrodespacer carried by Vsaid screw, said spacer' adapted to contact saidanvil and act against the tension of the disks to space the electrodesas the screw is. turned inwardly, and means for imparting minute motion`to said compensating electrode spacer. l y

8. A spark gap comprising a base having mounted thereon two sets ofopposing flexible disks, said disks concentrically mounted with respectto one another-,insulating assembling posts passing through all of saiddisks to maintain them in said concentric relationship, two concentricelectrode carriers oneV mounted centrally in each opposing set of disks,two opposing'electrodes each centrally secured in an electrode carrierand projecting therefrom to a contacting extent, an anvil carried byoneelectrode carrier, a screw carried by the other electrede carrier,said screw opposite to said anvil, a compensating electrode spacercarried by said screw, said spacer adapted to contact said anvil and actagainst the ten'- sion of the disks to space the electrodes as the screwis turned inwardly, a large gear wheel on the outer end ot said screw, a

small pinion in mesh .with said large gear wheel, a shaft adapted toturn said small pinion, and means adapted to turn the shatt andtransmitmotion to the electrode spacer through said speciiied reducedvmotion mechanism.

9. A spark gap comprising a base having mounted thereon two sets ofopposing flexible disks oi two each, said disks concentrically mountedwith respect to one another, three insulating assembling posts passingthrough all of said disksto maintain them in said concentricrelationship, two concentric electrode carriers each mounted centrallybetween the two disks of each opposing set, two opposing4 electrodeseach eentrallysecured in an electrode car wheel, a shaft adapted to turnsaid small pinion, a friction producing;v member asia ciated with saidshaft to prevent said shaft from being too easily turned, and :i knob onthe outer end of said shaft adapted to turn the saine and transmitmotion to the electrode spacer through said specified reduced motionmechanism.

In Witness whereof, I hereunto subscribe 20 lily IHUHB.

EDVIN S. FLARSHEIM.

